Rock cracker cartridges are known in prior art. SE 526830 discloses a cartridge which can be employed for cracking big rocks. The rock cracker cartridge is placed in a water filled drill hole, in which a chock wave is generated by means of a starting cartridge in the opening of the drill hole. The starting cartridge may be ignited manually by means of a rope at quite a short distance from the rock that shall be cracked. This well known cracker cartridge, as well as the system of which the cracker cartridge forms part, functions very well and is used to a considerable extent. The cartridge and the system, however, have some limitations. For example, electrical ignition can not be employed, and therefore neither delay blasting, i.e. blast set at intervals.
U.S. Pat. No. 5,763,816 discloses an explosive primer consisting of a container, which holds the explosive. Various explosives may be conceived, but in the first place the primer is intended to hold blasting gelatins and other high velocity explosives in a semiliquid or slurried form, which contain gellants and cross-linking agents in the explosive composition to gel inside the container to a desired consistency. The primer has a pierceable port, through which a detonator may be placed in direct contact with the explosive gel inside the container. In order to make this possible, the explosive gel either need to be compressed or not completely fill the container. It is not clear which of these alternatives that shall apply. However, the design of the primer disclosed requires that the detonator forcedly is pressed into a short tunnel and is caused to penetrate its bottom, which is weakened for that purpose, whereupon the detonator is pressed into the explosive charge which necessarily need either to be compressed or pressed aside to leave place for the detonator. This principle, however, makes assembling the primer a hazardous work. But unpriming the cartridge, a work which frequently need to be performed on working places, e.g. road working sites, would also be more or less hazardous, depending on the explosive that is employed, as the explosive will be exposed through the pierced port, once the detonator is withdrawn. If the explosive would consist of for example gun powder, as according to the present invention, it could run out, but also inhaling it from the open cartridge would be dangerous to health.